Nickel(II), Cadmium(II), and Copper(II) Complexes Based on Ditopic Terpyridine Derivative Ligand: Syntheses, Crystal Structures, and Luminescent Properties

Three complexes with the ditopic ligand 4-[4-(quinolin-8-yloxymethyl)phenyl]-2,2:6,2-terpyridine (abbreviated as L), [Ni(L)(2)](CH3COO)(2) (1), [Cd(L)(2)](ClO4)(2) (2), and [Cu-2(L)(2)](ClO4)(4)4DMF (3), were synthesized and characterized by elemental analysis, IR spectroscopy, and structurally analyzed by X-ray single-crystal diffraction. Interestingly, in complexes 1 and 2, two ligands adopt a tridentate chelating pattern where the oxaquinoline group is non-coordinated and coordinate with one M-II ion (M = Ni for 1, M = Cd for 2) to form a mononuclear unit. In complex 3, two ligands bridge two Cu-II ions by pyridyl N atoms, ethereal O atoms, and quinolyl N atoms in a head-to-tail mode to generate a dinuclear [Cu2L2] unit. Moreover, extended 1D and 2D supramolecular architectures are further constructed in 1-3 by multiple secondary interactions such as aromatic stacking and hydrogen bonding. Notably, the structural diversity of complexes 1-3 can be properly assigned to the central metal ions that have distinct coordination preferences. In addition, luminescent properties of the ligand and complex 2 were also investigated.